STEM teaching is expensive only if you buy everything. The free layer of STEM education — simulations, curricula, coding platforms, datasets, robotics alternatives — is now deep enough to run engaging units at every grade band without a purchase order. Here are 30 free STEM resources worth bookmarking in 2026, organized by what you teach.
Science Simulations & Virtual Labs
- PhET Interactive Simulations — the gold standard: hundreds of physics, chemistry, and math sims that run in any browser.
- NASA's education portals — mission data, imagery, lesson plans, and student challenges across earth and space science.
- NOAA education resources — weather, climate, and ocean data with classroom activities.
- Virtual dissections and anatomy tools — browser-based alternatives that solve budget and ethics in one move.
- Molecular viewers — free protein and molecule visualization for chemistry and biology.
- Smithsonian Science Education — free units and 3D-printable museum objects.
Coding & Computer Science
- Code.org — full K-12 CS curriculum, teacher training included, the default starting point.
- Scratch — block coding for elementary/middle creativity; the community remix culture is the curriculum.
- MIT App Inventor — real mobile apps with blocks; the "I made an actual app" effect is unmatched.
- CS First (Google) — themed Scratch units with videos, zero teacher CS background needed.
- Micro:bit classroom + simulator — physical computing that works even without the hardware via the browser simulator.
- Replit / browser IDEs — real Python and JavaScript with nothing installed — critical on locked-down Chromebooks.
Math
- Desmos — the graphing calculator plus a classroom activity platform teachers build careers on.
- GeoGebra — geometry, algebra, and 3D visualization with a massive shared activity library.
- Khan Academy — the practice backbone: mastery paths, videos, teacher dashboards.
- Open middle problems — the problem format that turns procedure into puzzling, free by design.
- Estimation and 3-act task collections — the community sites keeping math argument-rich at zero cost.
Engineering & Making
- Tinkercad — 3D design, circuits, and codeblocks in the browser; the on-ramp to CAD.
- NASA/engineering design challenge packs — structured build challenges from cheap materials.
- Paper-based engineering — bridge, tower, and glider challenge libraries: cardboard is a legitimate lab.
- Instructables education — project walkthroughs with teacher notes.
Data Science & Real Datasets
- Public data portals (census, weather, sports, health) — real questions beat toy datasets.
- Google Sheets + charts — the free data-science stack schools already have.
- CODAP — drag-and-drop data exploration built for classrooms.
Assessment & Review for STEM Classes
- Wayground — self-graded STEM review with math input and diagram questions; the library's science sections are deep (search tips), and homework mode handles spiral practice.
- AI question generators — draft concept checks from your unit text (workflow, passage-based version).
- Formative — show-your-work digital labs and problem sets (full toolkit).
Enrichment & Inspiration
- Citizen science projects — real research participation (bird counts, galaxy classification) from any classroom.
- STEM career video libraries — short "day in the life" clips that answer "when will we use this" with faces.
- Competition ladders — free-entry math, coding, and science olympiad prep materials that double as extension work.
Making Free Resources Stick
Free tools fail from abundance, not quality — pick one sim source, one practice platform, and one project format per semester, and wire them into your routine (bell ringers from Desmos or PhET screenshots; exit tickets after every lab). And if hardware is the gap, our grants guide covers the funding routes teachers actually win.
Frequently Asked Questions
Are these genuinely free or freemium traps?
Everything listed has a no-payment classroom path; a few (Khan, Wayground, Formative) sell upgrades that classrooms can ignore.
What about student accounts and privacy?
Most support join-without-account modes or Google SSO; check your district's approved list before rostering names.
Best single starting point for a new STEM teacher?
PhET + Desmos + Code.org covers sims, math, and CS with three bookmarks.
TheQuizizz.com is an independent guide and is not affiliated with any resource mentioned.